• Journal of the Korean Society for Aviation and Aeronautics
• /
• v.14 no.4
• /
• pp.66-73
• /
• 2006

This study focuses on the economies of launching regular air services between capital cities of South Korea and North Korea. The demand for traveling between these two cities is too small to justify scheduled air service. However, it may be possible to provide regular air service by utilizing via flight of incumbent Seoul-Beijing flights. There are numerous flight services between Seoul and Beijing and we may allow some of the Seoul-Beijing flights to stop by Pyung Yang for commercial traffic handling. This study tries to find the optimal discount rate which passengers traveling between Seoul and Beijing via Pyung Yang, the idea is reasonable considering the inconvenience of stopping at Pyung Yang. The Stated Preference Techniques are applied for the study. The required data were collected through interviews of passengers traveling from Seoul to Beijing. The major variables that are considered in flight choice are air fare, flying time, and flight frequency. The relative importance of these major variables is estimated by the logit models calibrated with stated preference data.

• Structural Engineering and Mechanics
• /
• v.75 no.6
• /
• pp.771-784
• /
• 2020

Reliability analysis techniques combining with various surrogate models have attracted increasing attention because of their accuracy and great efficiency. However, they primarily focus on the structures with continuous response, while very rare researches on the reliability analysis for structures with discontinuous response are carried out. Furthermore, existing adaptive reliability analysis methods based on importance sampling (IS) still have some intractable defects when dealing with small failure probability, and there is no related research on reliability analysis for structures involving discontinuous response and small failure probability. Therefore, this paper proposes a novel reliability analysis method called AGPC-IS for such structures, which combines adaptive Gaussian process classification (GPC) and adaptive-kernel-density-estimation-based IS. In AGPC-IS, an efficient adaptive strategy for design of experiments (DoE), taking into consideration the classification uncertainty, the sampling uniformity and the regional classification accuracy improvement, is developed with the purpose of improving the accuracy of Gaussian process classifier. The adaptive kernel density estimation is introduced for constructing the quasi-optimal density function of IS. In addition, a novel and more precise stopping criterion is also developed from the perspective of the stability of failure probability estimation. The efficiency, superiority and practicability of AGPC-IS are verified by three examples.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.27 no.9
• /
• pp.1492-1498
• /
• 2003

This study proposes a new conceptual Hybrid Electric Brake System (HEBS) which overcomes problems of a conventional hydraulic brake system. HEBS adopt a contactless type bake system when a vehicle speed is high, to obtain superior braking performances by eddy current. On the contrary, when a vehicle speed is low, HEBS employs a contact type brake system such as conventional hydraulic brake system to generate higher brake force. Therefore, HEBS transfers faster the braking intention of drivers and guarantees the safety of drivers. Braking torque analysis is performed by using a mathematical model which is proposed to investigate the characteristic of a vehicle dynamics when the brake torque is applied. Optimal torque control is achieved by maintaining a desired slip corresponding to the road condition. The results show that HEBS reduces the stopping distance, saves the electric energy, and increases the stability.

• Journal of the Korean Society of Safety
• /
• v.28 no.3
• /
• pp.23-28
• /
• 2013

This study focuses on finding ways to derive train's optimal ECO driving pattern, which can improve the ride quality and reduce driving energy consumption with keeping the time interval between the stations. As research method, we compared difference of currently operating train's ATO and MCS driving patterns, and concentrated upon the things need to consider in simulation in order to improve the existing pattern of ATO driving pattern's issues with securing the train operation safety. Determining driving pattern minimizing energy consumption by controlling powering within speed limit and controlling switching to coasting at appropriate point considering the track conditions for each section, and determining braking control starting time considering ride comfort and precise stopping is considered to be most important.

• Korea Trade Review
• /
• v.44 no.1
• /
• pp.31-44
• /
• 2019

This study examines the normalization of Korean GM management between the Korean government and GM in terms of external negotiation game and internal negotiation game using Putnam's Two-Level Games. In addition, GM's Win-set change and negotiation strategy were analyzed. This analysis suggested implications for the optimal negotiation strategy for mutual cooperation between multinational corporations and local governments in the global business environment. First, the negotiation strategy for Korea's normalization of GM management in Korea can be shifted to both the concession theory and the opposition theory depending on the situation change and the government policy centered on the cautious theory. Second, GM will maximize its bargaining power through 'brink-end tactics' by utilizing the fact that the labor market is stabilized, which is the biggest weakness of the Korean government, while maintaining a typical Win-set reduction strategy. GM will be able to restructure at any time in terms of global management strategy, and if the financial support of the Korean government is provided, it will maintain the local factory but withdraw the local plant at the moment of stopping the support. In negotiations on the normalization of GM management in Korea, it is necessary to prepare a problem and countermeasures for various scenarios and to maintain a balance so that the policy does not deviate to any one side.

• KSBB Journal
• /
• v.22 no.4
• /
• pp.197-200
• /
• 2007

This study examined the conditions of filtration and concentration of methanol extract from biomass. Filtration efficiency was improved by adding diatomaceous earth as a filter aid. The optimal amount of diatomaceous earth was 6% (w/w) to reduce the filtration time. The filtration time was reduced by 4.2% in first extraction, 30.0% in second extraction, 22.8% in third extraction, and 19.0% in fourth extraction, respectively. The optimal temperature of water bath was below 50$^{\circ}C$ for preventing paclitaxel degradation during concentration of methanol extract using a rotary evaporator. The temperature of concentrated solution in rotary evaporator was relatively low compared to bath temperature because of latent heat of evaporation. The stopping point of concentration in rotary evaporator for the following step was at a specific gravity of 0.96 of the concentrated solution in terms of the purity and yield of paclitaxel. This information is very useful for mass extraction of biomass for the recovery of paclitaxel from plant cell culture.

• Explosives and Blasting
• /
• v.38 no.4
• /
• pp.16-25
• /
• 2020

Multi-setting smart-investigation of the ground and large uncharged hole boring (MSP) method to reduce the blast-induced vibration in a tunnel excavation is carried out over 50m of long-distance boring in a horizontal direction and thus has been accompanied by deviations in boring alignment because of the heavy and one-directional rotation of the rod. Therefore, the deviation has been adjusted through the boring machine's variable setting rely on the previous construction records and expert's experience. However, the geological characteristics, machine conditions, and inexperienced workers have caused significant deviation from the target alignment. The excessive deviation from the boring target may cause a delay in the construction schedule and economic losses. A deep learning-based prediction model has been developed to discover an ideal initial setting of the MSP machine. Dropout, early stopping, pre-training techniques have been employed to prevent overfitting in the training phase and, significantly improved the prediction results. These results showed the high possibility of developing the model to suggest the boring machine's optimum initial setting. We expect that optimized setting guidelines can be further developed through the continuous addition of the data and the additional consideration of the other factors.

• Journal of Digital Convergence
• /
• v.13 no.10
• /
• pp.337-342
• /
• 2015

SMT is an equipment that picks up electronic components and does precise placing onto PCBs. In order to do this, it stops in front of a camera installed in the middle to go over vision inspection. And after that it is move for placing. There are 16 different types of routes in this process. This paper presents the fastest algorithm to place (sLa-Camera-pLb) among all these routes. In order to do this, instead of stopping in front of camera the object should move on while going over the vision inspection. Among all possible tracks, this thesis will provide algorithm to find out the fastest tracks to do vision inspection and placing. And as a result, this thesis have demonstrated that this method can save about 16% of time compared to going over inspection while the object is standing still through simulation.

• Transactions of the Korean Society of Automotive Engineers
• /
• v.16 no.1
• /
• pp.106-113
• /
• 2008

The starter motor noise is usually well identified by the customers since it is operated while the engine is quiet, and leaves distinct impressions of the vehicle. In this study the design of experiments(DOE) was applied to the identification of the noise sources of direct drive starter motor since this process usually requires lengthy analysis and elaborate experiments. In the first stage of the test, five controllable factors(alignment and dynamic unbalance of armature, tightening torques of T/bolt and center bracket bolt, and alignment of the center bracket-yoke-rear bracket), excluding static unbalance, are sorted out of all possible factors. Test results showed that the dynamic unbalance and misalignment of armature are the major factors. However, the error level of the first test was relatively high, indicating that there might be some missing major factors. In the second stage test the results showed that both static and dynamic unbalances are the dominant factors contributing to more than 80% of the overall noise, while the misalignment contributes around 12%. Error of the second test was about 4% that could be considered satisfactory. The noise level of the optimal product was predicted to be reduced by 19dBA, and verification test showed the average noise reduction of 16.8dBA with the standard deviation of 3.2dBA, and proved the usefulness of the whole DOE process.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.36 no.5
• /
• pp.465-475
• /
• 2012

This study was carried out with two goals. One was the development of a model of a wind turbine blade airfoil and the other was the application of this folding blade. In general, in large-sized (MW) wind turbines, damage is prevented because of the use of a pitch control system. On the other hand, pitch control is not performed in small wind turbines since equipment costs and maintenance costs are high, and therefore, the blade will cause serious damage. The wind turbine proposed in this study does not require maintenance, and the blades do not break during high winds because they are folded in accordance with changes in the wind speed. But generators are not cut-out, while maintaining a constant angle will continue to produce. The focus of this study, the wind turbine is continued by folding blade system in strong winds and gusts without stopping production.